SAXS STUDY ON THE CYTOPLASMIC CUBCOMPLEX FROM THE VIBRIO CHOLERAE TYPE 2 SECRETI

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Pathogenic bacteria such as Vibrio cholerae employ Type II Secretion Systems for the export of their infections agent such as cholera toxin through the outer membrane. While the pore is located in the outer membrane, the system is energized by a cytoplasmic secretion ATPase (EpsE). EpsE is linked to the rest of the system via the bitopic inner membrane protein EpsL. Various reports from related systems, e.g. Type III Secretion, Type IV Pili, indicate that nucleotide binding has a dramatic effect on the oligomeric state of EpsE, and that the oligomeric state has an effect on the ATPase activity. However, there are indications that the oligomerization pattern of EpsE in complex with the cytoplasmic domain of EpsL (cyto-EpsL) differs from the current dogma. We have evidence that EpsE (E) and cyto-EpsL (cL) form oligomeric assemblies at minimum E2cL2, and likely E6cL6, in the presence of nucleotides. We propose to conduct solution x-ray scattering studies to investigate these assemblies as a function of different nucleotides, Mg as well as of temperature to complement our on-going crystallographic studies on this system. Our aim is to identify the physiologically relevant form of assemblies and find solution condition to stabilize it for higher resolution studies.